Flight control system including automatic altitude locking means

ABSTRACT

A flight control system includes a manually operated pitch command selector arranged for automatically engaging and locking the system in an altitude hold mode when pitch command is zero to eliminate pilot engagement of said altitude hold mode.

United States Patent Hofmeister 1 May 30, 1972 [541 FLIGHT CONTROLSYSTEM 2,873,418 2/1959 Owen ..244/77 0 x INCLUDING AUTOMATIC ALTITUDE3,062,486 Il/l962 Shepherd .244 77 SE NG IE S 3,002,7[3 10/1961 Noxon eta]. ....244/77 SE LOCK! AN 2,633,315 3/1953 Rossire ..244/77 D [72]Invent r: L u n l t Fel'fldale, Mich. 2,975,35l 3/1961 Wegley 1 ..244/77D X [73] Asian: The Bendix Corponflon 3,079,109 2/ 1963 Jude et al...244/77 SE [22] Filed: May 15, 1970 Primary Examiner-Milton BuchlerAssistant ExaminerJeffrey L. Forman [2]] Appl' 37550 Attorney-Flame,Arens, Hartz, Smith 81: Thompson, Bruce L.

Lamb and William G. Christoforo [52] US. Cl. ..244/77 D, 244/77 SE,318/584 [51] Int. Cl. ..B64c 13/18 [57] ABSTRACT [58] new Search 77 77 Aflight control system includes a manually operated pitch commandselector arranged for automatically engaging and locking the system inan altitude hold mode when pitch com- [56] References Cited mand is zeroto eliminate pilot engagement of said altitude UNITED STATES PATENTShold mode- 2,889,509 6/1959 Gorzelany et a]. ..244/77 D X 2 Claims, 3Drlwlng Figures I PITCH CONTROLLER f /20 22 I6 ALTITUDE FLIGHT SERVOPOWER CONTROLLER COMPUTER SYSTEM SUPPLY 1 1 -F ELEVATOR FLIGHT CONTROLSYSTEM INCLUDING AUTOMATIC ALTITUDE LOCKING MEANS BACKGROUND OF THEINVENTION 1. Field of the Invention This invention relates to aircraftcontrol systems and particularly, to systems for controlling the craftin pitch command and altitude hold modes of flight. More particularly,this invention relates to systems of the type described wherein pilotwork load is reduced.

2. Description of the Prior Art Modern automatically controlled aircraftrequire that the pilot sequentially perform many operations for safelyarriving at a given destination. As more sophisticated equipment isadded to the control system, the ability of the pilot to efficiently andsafely perform these operations is approaching a limit.

In order to reduce the pilot's work load, it is desirable to eliminatepilot engagement of certain flight modes while retaining these modes inthe control system. To this end, the present invention provides meansfor automatically engaging and locking the control system in thealtitude hold mode of flight when pitch command is zero and eliminatespilot engagement of said altitude hold mode.

SUMMARY OF THE INVENTION A flight control system includes a pitchcommand selector having a thumb wheel which is accessible to the pilotfor commanding pitch attitude. The thumb wheel is arranged for actuatinga switch to operate an altitude controller. When the thumb wheel is inany position other than zero pitch, the switch is actuated to disengagethe altitude controller. When the thumb wheel is in zero pitch position,the switch is actuated to engage the altitude controller, whereby thecontrol system locks in the altitude hold mode of flight.

One object of this invention is to provide a system for automaticallycontrolling an aircraft in pitch command and altitude hold modes offlight.

Another object of this invention is to reduce pilot work load inoperating said system by automatically engaging the altitude hold modeof flight when pitch command is zero.

Another object of this invention is to arrange a pitch command selectorfor automatically engaging and locking the control system in thealtitude hold mode when pitch command is zero and for disengaging thealtitude hold mode when the pitch command is other than zero.

The foregoing and other objects and advantages of the in vention willappear more fully hereinafter from a consideration of the detaileddescription which follows, taken together with the accompanying drawingswherein one embodiment of the invention is illustrated by way ofexample. It is to be expressly understood, however, that the drawingsare for illustration purposes only and are not to be construed asdefining the limits of the invention.

DESCRIPTION OF THE DRAWINGS FIG. 1 is a block diagram showing anaircraft control system in accordance with the invention.

FIG. 2 is a diagrammatic representation showing a pitch command selectorarranged for disengaging the altitude hold mode of flight.

FIG. 3 is a diagrammatic representation showing the pitch commandselector arranged for engaging the altitude hold mode of flight.

DESCRIPTION OF THE INVENTION FIG. 1 shows a pitch command selectordesignated generally by the numeral 1 and including a pitch controller 2manually operated by a thumb wheel 4. Thumb wheel 4 protrudes from aninstrument panel 6 so as to be accessible to the pilot for commandingthe pitch attitude of an aircraft. Thumb wheel 4 has, for purposes whichwill be hereinafter described, a notch or groove 8 opposite the zeropitch or center position, and which position is indicated on thumb wheel4 by an inscribed line 10.

Thumb wheel 4 is coupled to a switch 12. When the thumb wheel is in anyposition other than zero pitch, switch 12 is maintained in the openposition to disconnect an aircraft power supply 16 from an altitudecontroller 18. With power supply 16 so disconnected, altitude controller18 is ineffective for controlling the aircraft. During this time thepitch attitude of the craft is controlled by pitch controller 2 whichprovides a signal corresponding to the commanded pitch. The pitchcommand signal is applied to a flight computer 20 which provides anelevator control signal. The elevator control signal is applied to aservo system 22 which is connected by suitable mechanical means toelevator I4 for operating the elevator in accordance with the controlsignal.

When thumb wheel 4 is in zero pitch position (FIG. 3) switch 12 isclosed thereby connecting power supply 16 to altitude controller 18 forenergizing the altitude controller. Altitude controller 18 provides analtitude command signal which is applied to flight computer 20 forproviding an elevator control signal, and the elevator control signaldrives servo system 22 for operating elevator 14 to maintain theaircraft at a desired altitude.

Pitch selector 1, altitude controller 18, flight computer 20 and servosystem 22 are devices well known in the art and it is not deemednecessary, for purposes of describing the present invention, to fullydescribe their operation.

By way of illustration only, pitch selector 1 may be a device such asdescribed in U.S. Pat. No. 2,879,015 to Ardia, and which patentdescribes a controller including a manually operated thumb wheel forchanging the pitch attitude of the craft.

Altitude controller 18 may be a device including an altitude sensor, andwhich device automatically maintains an aircraft at a desired altitudelevel such as described in U.S. Pat. No. 2,512,902 to Rossire.

Likewise, flight computer 20 may be a device which takes into accountvarious parameters for providing a controlling output to give optimumaircraft performance. A computer of this type is described in U.S. Pat.No. 2,950,076 to Shirey, et al.

Servo system 22 is of the type including a servo amplifier, a servomotor for driving a rate generator and appropriate follow-up means suchas described in the aforenoted U.S. Pat. No. 2,879,015.

All of the aforenoted patents are assigned to The Bendix Corporation,assignee of the present invention.

FIGS. 2 and 3 show a preferred embodiment of the invention wherein thumbwheel 4 is, in effect, a cam for actuating a plunger 32 of aconventional and commercially available micro-switch 30. Micro-switch 30has a pair of input conductors 34 and 36 leading to power supply 16 anda pair of output conductors 38 and 40 leading to altitude controller 18,said power supply and altitude controller being shown in FIG. I.

With specific reference now to FIG. 2, when thumb wheel 4 is in anyposition other than zero pitch as shown in the figure, plunger 32 isdepressed holding switch 30 open and disconnecting power supply 16 fromaltitude controller 18. When thumb wheel 4 is in the zero pitchposition, (FIG. 3) switch plunger 32 drops into notch 8 on thumb wheel 4closing switch 30 and connecting power supply 16 to altitude controllerl8.

The obvious advantage to the system of the invention is that to engagethe altitude hold mode of flight no efi'ort is required from the pilotother than operation of pitch command selector 1. After take-off andupon engagement of the automatic control system, the pilot selects adesired pitch angle through thumb wheel 4 and the aircraft continues toascend or descend, as the case may be, until the desired altitude isreached, and whereupon the pilot has two options. One, the pilot cancenter thumb wheel 4, thereby bringing the craft back to the altitude atwhich the command was centered or two, he can smoothly roll thumb wheel4 to zero pitch (level flight) whereupon altitude controller 18 willengage and the system will be locked in the altitude hold mode. in bothcases the pilot does not have to engage the altitude hold mode afterleveling.

Although only one embodiment of the invention has been illustrated anddescribed, various changes in the form and relative arrangements of theparts, which will now appear obvious to those skilled in the art may bemade without departing from the scope of the invention. Reference is,therefore, to be had to the appended claims for a definition of thelimits of the invention.

What is claimed is:

1. An aircraft control system comprising:

means selectively operated by the pilot for commanding the aircraftattitude;

first means in cooperative arrangement with the pilot operated means forproviding a first signal corresponding to the selected command;

a power supply a signal device for generating a second signalcorresponding to the displacement of the crafl from a reference when thesignal device is connected to the power supply;

a switch connecting the power supply to the signal device when theswitch is closed, the switch including a movable member, with the switchbeing opened to disconnect the power supply from the signal device whenthe movable member is in a first position and closed when the member isin a second position, the pilot operated means providing a cam surfacewith the movable switch member riding thereon, and the cam surface beingarranged to displace the movable member from the first to secondposition when the pilot operated means is selectively operated tocommand zero attitude;

control signal means connected to the first means and to the signaldevice for providing a first control signal in response to the firstsignal and for providing a second control signal in response to thesecond signal; and

control means connected to the control signal means and responsive tothe first control signal for controlling the attitude of the craft, andresponsive to the second control signal for controlling the craft tohold at the displacement from the reference.

2. An aircraft control system comprising:

command signal means including a thumb wheel selectively positioned bythe pilot of the craft for commanding pitch attitude and having a grooveopposite the zero pitch posi' tion, and means operably connected to thethumb wheel for providing a signal corresponding to the selected pitchcommand;

a power supply;

an altitude controller;

a normally open switch connecting the power supply to the altitudecontroller and including a movable member in a first position when theswitch is open and in a second position when the switch is closed, andsaid thumb wheel and switch being so arranged that when zero pitchcommand is selected the movable switch member drops into the groove onthe thumb wheel to move from the first position to the second positionto close said switch and to connect the power supply to the altitudecontroller for rendering said controller effective for providing asignal corresponding to the altitude of the craft;

control signal means connected to the command signal means and to thealtitude controller for providing a first control signal in response tothe command signal and for providing a second control signal in responseto the altitude signal; and

control means connected to the control signal means and responsive tothe first control signal for controlling the pitch of the craft andresponsive to the second control signal for controlling the craft tohold at the zero pitch altitude.

I I II I I

1. An aircraft control system comprising: means selectively operated bythe pilot for commanding the aircraft attitude; first means incooperative arrangement with the pilot operated means for providing afirst signal corresponding to the selected command; a power supply asignal device for generating a second signal corresponding to thedisplacement of the craft from a reference when the signal device isconnected to the power supply; a switch connecting the power supply tothe signal device when the switch is closed, the switch including amovable member, with the switch being opened to disconnect the powersupply from the signal device when the movable member is in a firstposition and closed when the member is in a second position, the pilotoperated means providing a cam surface with the movable switch memberriding thereon, and the cam surface being arranged to displace themovable member from the first to second position when the pilot operatedmeans is selectively operated to command zero attitude; control signalmeans connected to the first means and to the signal device forproviding a first control signal in response to the first signal and forproviding a second control signal in response to the second signal; andcontrol means connected to the control signal means and responsive tothe first control signal for controlling the attitude of the craft, andresponsive to the second control signal for controlling the craft tohold at the displacement from the reference.
 2. An aircraft controlsystem comprising: command signal means including a thumb wheelselectively positioned by the pilot of the craft for commanding pitchattitude and having a groove opposite the zero pitch position, and meansoperably connected to the thumb wheel for providing a signalcorresponding to the selected pitch command; a power supply; an altitudecontroller; a normally open switch connecting the power supply to thealtitude controller and including a movable member in a first positionwhen the switch is open and in a second position when the switch isclosed, and said thumb wheel and switch being so arranged that when zeropitch command is selected the movable switch member drops into thegroove on the thumb wheel to move from the first position to the secondposition to close said switch and to connect the power supply to thealtitude controller for rendering said controller effective forproviding a signal corresponding to the altitude of the craft; controlsignal means connected to the command signal means and to the altitudecontroller for providing a first control signal in response to thecommand signal and for providing a second cOntrol signal in response tothe altitude signal; and control means connected to the control signalmeans and responsive to the first control signal for controlling thepitch of the craft and responsive to the second control signal forcontrolling the craft to hold at the zero pitch altitude.